Wintry blast on the way

A vigorous cold front is preparing to burst its way up the South Island this afternoon, bringing plunging temperatures, squally winds and even hail and thunder in some places.

The front will be similar to the one that brought massive wind gusts and hail to the Marlborough coast and Wellington last Friday, but forecasters believe it will peak further south this time, over coastal mid- and South Canterbury an hour or so either side of 6pm.

On current thinking the cold change should reach Christchurch between 7pm and 8pm, with predicted thunderstorms, temperatures falling to single figures and southerly winds gusting as high as 110km/h.

The Press online wants to hear from you when the cold front passes your place and about what weather it brings.

MetService spokesman Bob McDavitt said it would be a "humdinger'' of a change. Thunderstorms were highly likely along the cold front between about Oamaru and Cheviot, with a risk of rainfall rates of up to 20mm an hour, hail between 5mm and 15mm in diameters and gusts to 110km/h.

"This one's going to peak around 4 to 6pm over north Otago and south and central Canterbury, that's the current timing.

With a good nor'west ahead of it, temperatures should rise in Christchurch to 24 degrees Celsius this afternoon, ease to around 20C after sunset then drop to single digits with the southerly change.'' The nor'wester should arrive in Canterbury in the early afternoon.

While the front was highly active, it was fortunately arriving at a generally quieter time of year around the autumn equinox, he said.

"The other [spring] equinox is when you get the strongest temperature gradients between land and sea which cause the most violent changes.''

At 10.30am the front was moving across Stewart Island heading for the Southland coast.

Has the cold front hit you yet? Let us know what the weather is doing at your place, email reporters@press.co.nz

- © Fairfax NZ News